Natural selectionis the differential survival and reproduction of individuals due to differences inphenotype; it is a key mechanism ofevolution. The term “natural selection” was popularised byCharles Darwin, who intended it to be compared with artificial selection, now more commonly referred to asselective breeding.

Variationexists within allpopulationsoforganisms. This occurs partly because randommutationsarise in thegenomeof an individual organism, and these mutations can be passed tooffspring. Throughout the individuals’ lives, their genomes interact with their environments to cause variations intraits. (The environment of a genome includes the molecular biology in thecell, other cells, other individuals, populations,species, as well as the abiotic environment.) Individuals with certain variants of the trait may survive and reproduce more than individuals with other, less successful, variants. Therefore, the population evolves. Factors that affect reproductive success are also important, an issue that Darwin developed in his ideas onsexual selection, which was redefined as being included in natural selection in the 1930s when biologists considered it not to be very important,andfecundity selection, for example.

Natural selection acts on the phenotype, or the observable characteristics of an organism, but thegenetic(heritable) basis of any phenotype that gives a reproductive advantage may become more common in a population (seeallele frequency). Over time, this process can result in populations that specialise for particularecological niches(microevolution) and may eventually result in the emergence of new species(macroevolution). In other words, natural selection is an important process (though not the only process) by which evolution takes place within a population of organisms. Natural selection can be contrasted with artificial selection, in which humansintentionally choose specific traits (although they may not always get what they want). In natural selection there is no intentional choice. In other words, artificial selection isteleologicaland natural selection is not teleological.

Galileo

The Galileo affair was a sequence of events, beginning around 1610, culminating with the trial and condemnation of Galileo Galilei by the Roman Catholic Inquisition in 1616 and 1633 for his support of heliocentrism.

In 1610, Galileo published his Sidereus Nuncius (Starry Messenger), describing the surprising observations that he had made with the new telescope, namely the phases of Venus and the Galilean moons of Jupiter. With these observations he promoted the heliocentric theory of Nicolaus Copernicus (published in De revolutionibus orbium coelestium in 1543). Galileo’s initial discoveries were met with opposition within the Catholic Church, and in 1616 the Inquisition declared heliocentrism to be formally heretical. Heliocentric books were banned and Galileo was ordered to refrain from holding, teaching or defending heliocentric ideas.

Galileo began his telescopic observations in the later part of 1609, and by March 1610 was able to publish a small book, The Starry Messenger (Sidereus Nuncius), relating some discoveries that had not been dreamed of in the philosophy of the time: mountains on the Moon, lesser moons in orbit around Jupiter, and the resolution of what had been thought to be very cloudy masses in the sky (nebulae) into collections of stars too faint to see individually without a telescope. Other observations followed, including the phases of Venus and the existence of sunspots.

Galileo’s contributions caused difficulties for theologians and natural philosophers of the time, as they contradicted scientific and philosophical ideas based on those of Aristotle and Ptolemy and closely associated with the Catholic Church (despite their being pagans). In particular, Galileo’s observations of the phases of Venus, which showed it to circle the sun, and the observation of moons orbiting Jupiter, contradicted the geocentric model of Ptolemy and supported the Copernican model advanced by Galileo.

Jesuit astronomers, experts both in Church teachings, science, and in natural philosophy, were at first skeptical and hostile to the new ideas; however, within a year or two the availability of good telescopes enabled them to repeat the observations. In 1611, Galileo visited the Collegium Romanum in Rome, where the Jesuit astronomers by that time had repeated his observations. Christoph Grienberger, one of the Jesuit scholars on the faculty, sympathized with Galileo’s theories, but was asked to defend the Aristotelian viewpoint by Claudio Acquaviva, the Father General of the Jesuits. Not all of Galileo’s claims were completely accepted: Christopher Clavius, the most distinguished astronomer of his age, never was reconciled to the idea of mountains on the Moon, and outside the collegium many still disputed the reality of the observations. In a letter to Kepler of August 1610, Galileo complained that some of the philosophers who opposed his discoveries had refused even to look through a telescope:

My dear Kepler, I wish that we might laugh at the remarkable stupidity of the common herd. What do you have to say about the principal philosophers of this academy who are filled with the stubbornness of an asp and do not want to look at either the planets, the moon or the telescope, even though I have freely and deliberately offered them the opportunity a thousand times? Truly, just as the asp stops its ears, so do these philosophers shut their eyes to the light of truth.

Galileo became involved in a dispute over priority in the discovery of sunspots with Christoph Scheiner, a Jesuit. This became a bitter lifelong feud. Neither of them, however, was the first to recognise sunspots—the Chinese had already been familiar with them for centuries.

At this time, Galileo also engaged in a dispute over the reasons that objects float or sink in water, siding with Archimedes against Aristotle. The debate was unfriendly, and Galileo’s blunt and sometimes sarcastic style, though not extraordinary in academic debates of the time, made him enemies. During this controversy one of Galileo’s friends, the painter, Lodovico Cardi da Cigoli, informed him that a group of malicious opponents, which Cigoli subsequently referred to derisively as “the Pigeon league,” was plotting to cause him trouble over the motion of the earth, or anything else that would serve the purpose. According to Cigoli, one of the plotters had asked a priest to denounce Galileo’s views from the pulpit, but the latter had refused. Nevertheless, three years later another priest, Tommaso Caccini, did in fact do precisely that.

Intell I.D.

Intelligent design (ID) is the pseudoscientific view that “certain features of the universe and of living things are best explained by an intelligent cause, not an undirected process such as natural selection.” Educators, philosophers, and the scientific community have demonstrated that ID is a religious argument, a form of creationism which lacks empirical support and offers no tenable hypotheses. Proponents argue that it is “an evidence-based scientific theory about life’s origins” that challenges the methodological naturalism inherent in modern science, while conceding that they have yet to produce a scientific theory. The leading proponents of ID are associated with the Discovery Institute, a politically conservative think tank based in the United States. Although they state that ID is not creationism and deliberately avoid assigning a personality to the designer, many of these proponents express belief that the designer is the Christian deity.

ID presents negative arguments against evolutionary explanations, and its positive argument is an analogy between natural systems and human artifacts, a version of the theologicalargument from design for the existence of God. Both irreducible complexity and specified complexity present detailed negative assertions that certain features (biological and informational, respectively) are too complex to be the result of natural processes. Proponents then conclude by analogy that these features are evidence of design. Detailed scientific examination has rebutted the claims that evolutionary explanations are inadequate, and this premise of intelligent design—that evidence against evolution constitutes evidence for design—has been criticized as a false dichotomy.